Police on high alert after renewed threats from Islamic State

Security experts are concerned that the recent attacks in France may inspire copycat attacks in the US and elsewhere. Some officials aren't convinced that the Islamic State threat is now worse, although others see potential risks.

Law enforcement officials across the United States are on heightened alert Monday after a September 2014 message from the Islamic State (IS) was rereleased, telling followers to “rise up and kill intelligence officers, police officers, soldiers, and civilians.” The threat called for attacks against the US, France, Australia, and Canada.

Security experts are now concerned that the recent attacks in France by those who include at least one self-proclaimed IS supporter may inspire copycat attacks. Since last week’s attacks in Paris against satirical magazine Charlie Hebdo, police officers, and a kosher grocery store, IS supporters have taken advantage of the fervor to encourage further violence.

But while the Federal Bureau of Investigation and the Department of Homeland Security issued bulletins requesting that law enforcement and military personnel throughout the US remain especially alert, some officials aren't convinced the threat is now worse.

“I don’t think that we are under any more threat ... or under any less threat than we were the day before,” John Miller, the New York Police Department's deputy commissioner for counterterrorism, said Sunday on CBS’s “Face the Nation” program.

In an interview with ABC News’s George Stephanopoulos, Attorney General Eric Holder said there is no concrete threat he can point to, although he sees how the security environment could be more precarious than in previous years.

“We have a very small number of people, without huge amounts of planning, without huge amounts of resources, inflicting very severe damage,” Mr. Holder stated.

Meanwhile, some do think that the recent attacks in France could make it more dangerous for both law enforcement officials and civilians in the US. An internal NYPD memo called for the rereleased video and other recent IS threats to be taken more seriously “in light of the terror attacks in France.”

“Pay close attention to people as they approach and look for their hands as they approach you,” read the memo, obtained by the New York Daily News.

Police officers have already been extra vigilant following recent attacks against NYPD and other officers amid racial tensions.

On CNN’s "State of the Union" program, Sen. Dianne Feinstein (D) of California, vice chairman of the Senate Intelligence Committee, said that attacks on the US could take place because of the possible presence of IS-affiliated groups that have remained inactive until now.

“I think there are sleeper cells, not only in France but certainly in other countries and, yes, in our own,” she said.

An earlier bulletin issued by the FBI, at the end of last year, warns of "individuals overseas spotting and assessing individuals in the U.S. based on their social media postings in support of the group.”

In July, Matthew Olsen, then director of the National Counterterrorism Center, estimated that more than 1,000 Westerners, including about 100 Americans, have traveled to Syria to fight with extremist groups, many of which are affiliated with IS.

Individuals with passports from Western countries can travel between Syria and the US with relative ease. John McLaughlin, former deputy director of the Central Intelligence Agency, told "PBS NewsHour" this weekend that there is now a larger number of extremists holding Western passports than at any time in history.

The video that was rereleased opens with news clips of President Obama and British Prime Minister David Cameron discussing IS. IS spokesman Abu Mohammed al-Adnani then goes on to encourage supporters who do not have access to an improvised explosive device or gun to carry out attacks using whatever means available, such as "[slaughtering] him with a knife or [running] him over with your car.”